1. Musculoskeletal MRI

2. Goals
What types of MR studies are available for evaluation of the musculoskeletal system?
Considerations when ordering a study
Remember one of the roles of the radiologist is as consultant to work with you in determining the best study for the patient’s needs (it’s in the job description)… talk to them!
Most common pathologies for which MSK MRI is performed

3. Exam Types MRI without contrast MRI with contrast MR Arthrogram
Most common
Evaluation of ligaments, tendons, occult fracture, cartilage
MRI with contrast
Evaluation of bone or soft tissue tumor, osteomyelitis, abscess
MR Arthrogram
Evaluation of labrum, intercarpal ligaments

4. Body Part
When ordering any study must have a ddx in mind, particularly with MRI (not a screening tool)
Cannot perform an MRI of a whole extremity (time, pt motion, protocol issues)
Must identify part to be imaged – be specific
A joint, a bone (prox, mid, distal), a muscle (origin, belly, insertion)
Must have plain radiograph
FOV about 25cm.

5. Most Common Indications
Occult fx or stress fx
Early osteonecrosis – in pt with risk factors & pain, known AVN of one hip
Osteomyelitis – plain film is insensitive (30-50% loss of bone density) BUT necessary for MRI interpretation, nucs has poor resolution
Osteochondral lesion – evaluate stability
Ligament/tendon injury – knee, shoulder, ankle > other jts
Bone tumor – MUST HAVE X-RAY 1st, imperative in providing ddx on MRI (dx on x-ray, determine extent on MR)
Soft tissue mass/muscle injury

6. Considerations when ordering an MRI
Joint replacement in joint of interest – don’t do it
Pacemaker – don’t do it
Claustrophobia - sedation
Unable to hold still/follow instructions – sedation
Metal in area of interest (susceptibility artifact) – consult radiologist, may vary technique or recommend another study
Metal not in area of interest ie. orbits (motion, overheating)
If you only remember one thing, remember this:
cannot do a PE protocol chest CT without contrast

7. Metal Artifact
Small metal foreign body results in large area of signal void.
Metal or gas = black hole.

8. General Principles Fluid, edema, inflammation is bright on T2
Fat is bright on T1 & T2 (can have fat sat)
Blood is often bright on T1
Tendons & ligaments are black on all sequences
Cartilage is bright on T2
Muscle is intermediate in signal
Do not order an MRI for necrotizing fasciitis.

9. Pelvis & Hip – Normal Anatomy
Joints – sacroiliac, pubic symphysis, hips
Tendons – iliopsoas, gluteal, hamstrings, rectus femoris
Bursa – trochanteric, iliopsoas
Bones – evaluate for bone marrow replacing process (MM, mets), AVN, occult or stress fx
Acetabular labrum – need intra-articular gadolinium

10. Femoral Head Osteonecrosis
Groin pain
Many predisposing factors: trauma (fem neck fx, dislocation), steroids, SLE, sickle cell dz, pancreatitis, alcohol abuse, Gaucher’s dz
Increased risk of contralateral AVN, must evaluate other side, most sensitive study is MRI
MRI:
Early – bone marrow edema
Later – geographic area of abnormal signal in the anterosuperior femoral head; double line sign on T2
Even later – subchondral collapse, femoral head collapse, degenerative joint dz
Double line sign – indicates ischemic necrosis, inner line of high signal surrounded by a line of low signal, interface of dead and living bone, may be chemical shift artifact

11. Femoral Head Osteonecrosis

12. the other hip – 40% bilateral
Anterior and superior femoral head

13. More examples of AVN

14. and more…
Triple line sign?

15. Labral Tear Clicking, locking, pain with pivoting/twisting
Traumatic (young), degenerative (older) or assoc. with femoroacetabular impingement (middle-aged)
MRI:
Anterosuperior or posterosuperior
Linear high T2 signal
Loss of triangular morphology
Paralabral cyst
MR arthrogram most sensitive study – contrast fills tear
Femoroacetabular impingement – repetitive microtrauma from impingement of femoral head against acetabulum, associated with labral tears and cartilage defects, focal acetabular chondral lesions, focal underlying subchondral sclerosis, edema, cystic change

16. Knee – Normal Anatomy Anterior & posterior cruciate ligaments
Medial & lateral menisci
Medial collateral ligament
Lateral ligamentous complex (lateral collateral, iliotibial band, biceps femoris)
Extensor mechanism
Normal variant (discoid meniscus)

17. Knee – Normal Anatomy

18. ACL Tear
Sports injury, rapid stopping/starting/pivoting (skiing, soccor, football, basketball etc), anterior drawer sign on PE
MRI:
Disruption of fibers, high signal on T2
Pivot-shift contusions
Anterior translation of tibia relative to femur
Associated with MCL and medial meniscus injury – O’Donahue’s unhappy triad
Associated with Segond fx (avulsion of mid third lateral capsular ligament from lateral tibial plateau)

19. ACL Tear

20. ACL Tear – Pivot shift contusion

21. PCL Tear Dashboard injury of flexed knee, posterior drawer sign on PE
MRI:
Disruption of fibers/thickened fibers
Abnormal high T2 signal
Avulsion at insertion on posterior tibia

22. PCL Tear

23. Meniscal Tear Joint line tenderness, clicking, locking MRI:
High T2 signal in the meniscus extending to the articular surface
longitudinal, radial, flap (flipped), oblique, bucket-handle
Parameniscal cyst

24. Oblique Undersurface Tear w/ Parameniscal Cyst

25. Bucket-handle Tear Medial > lateral Diminutive meniscus
Inner edge of meniscus is displaced medially into notch
Double PCL sign

26. Bucket-handle Tear

27. Discoid Meniscus
Predisposes to early degeneration and tear of meniscus
Lateral >> medial
MRI:
Large meniscus, no longer C-shaped
Bowtie should not be seen on ≥3 consecutive sagittal images (4mm)

28. Discoid Meniscus

29. Medial Collateral Ligament Tear
Valgus stress
Complete or partial tears affecting superficial and/or deep fibers
MRI:
Disruption of fibers with thickening & abnormal high signal
Associated with ACL & medial meniscal tears
Pellegrini-Stieda lesion – ossification at origin of MCL indicative of old tear
Superficial fibers – medial collateral ligament proper
Deep fibers – meniscofemoral & meniscotibial attachemnts

30. Medial Collateral Ligament Tear
Pellegrini-Stieda lesion
Indicates old MCL tear
Ossification at origin of MCL from medial femoral condyle

31. Acute on chronic MCL tear

32. Patellar Tendon Tear Partial or complete
Most commonly in proximal third of tendon at inferior pole of patella
Plain film:
patella alta
MRI:
Disruption of fibers, thickening & abn signal
Fluid-filled gap, hemorrage or granulation tissue

33. Patellar Tendon Tear

34. Patellar Tendon Tear different patient

35. Jumper’s Knee (Patellar Tendinosis)
Repetitive trauma
MRI:
Proximal third of patellar tendon (posterior fibers)
Early – edema in peritenon
Later - thickening & edema (inc T2)
Even later – partial or complete tear
+/- reactive osteitis in lower pole patella (edema)
Reactive edema in adjacent fat pad

36. Jumper’s Knee
Suprapatellar effusion. Normal lucency of Hoffa’s fat pad is obscured.

37. Jumper’s Knee

38. Osteochondral Lesion Young male, 50% have h/o trauma
Lateral aspect of medial femoral condyle, talar dome, capitellum
Plain film: area of sclerosis or bone/cartilage fragment in situ or defect with loose body in joint
MRI necessary to determine stability and guide treatment (stable-heal spontaneously, unstable-surgery)
MRI:
Fragment composed of hyaline articular cartilage and underlying subchondral bone
Unstable if fluid between fragment and donor site on T2

39. OCD

40. OCD

41. Ankle – Normal Anatomy
Joints – tibiotalar, distal tibiofibular, subtalar (ant, middle, post), intertarsal
Tendons – flexor (tibialis posterior, digitorum longus, hallucis longus), extensor (tibialis anterior, hallucis longus, digitorum), peroneus (longus, brevis), Achilles
Ligaments – medial (deltoid), lateral (talofibular, talocalcaneal), syndesmotic, Lis-Franc
Muscles, bones, plantar fascia
Normal Variants – plantaris, accessory soleus
Tom Dick & Harry
Tom Hates Dick
Plantaris muscle tendon runs along side the achilles in 90% of people, can be mistaken for achilles tendon tear.

42. Tarsal Coalition Lack of segmentation of two tarsal bones
Most commonly calcaneonavicular or talocalcaneal (middle subtalar joint)
20% bilateral; pain, flat foot
Cartilaginous, fibrous, osseous
Plain film: anteater sign, continuous C sign, talar beak, pes planus
MRI:
Cartilaginous, fibrous or bony bridge between 2 tarsal bones
Fibrous/cartilaginous - JSN, irregularity, sclerosis, bone marrow edema
Bony – continuity of bone marrow and cortex

43. Talocalcaneal Coalition

44. Calcaneonavicular Coalition

45. Calcaneonavicular Coalition

46. Accessory Soleus Muscle

47. Accessory Soleus

48. … and OCD
Stable or unstable?

49. Peroneus Brevis Split Tear
Peroneus brevis is normally round and anterior to longus
Tear most commonly at level of lateral malleolus
MRI:
C-shaped tendon
Longitudinal split, peroneus longus may be interposed between two subtendons
+/- fluid in tendon sheath (tenosynovitis)

50. Peroneus Brevis Split Tear
Tom
Talar dome
Dick
Harry
Peroneus
tendons
Achilles

51. Stress Fracture 2 types of stress fractures:
Fatigue fx – normal bone under abnormal stress (young marathon runner, military recruit etc…)
Insufficiency fx – abnormal bone under normal stress (elderly osteopenic female, steroids etc…)
Characteristic locations: 3rd metatarsal, tibial diaphysis, calcaneus, medial aspect femoral neck, sacrum
Plain film:
Cortical bone – periosteal rxn and/or endosteal thickening
Cancellous bone - ill-defined sclerosis
MRI:
Low signal line on T1
High signal bone marrow edema on T2
Calcaneus – trabecular fractures perpendicular to long axis

52. Stress Fracture
Hx: 28 yo female training for marathon. Pain with running, stopped with rest.
Note normal residua of growth plate.

53. Stress Fracture

54. Stress Fracture
Compare to normal physeal line.

55. Brachial Plexus – Normal Anatomy
Ventral nerve roots of C5, C6, C7, C8 & T1
Coarse between anterior & middle scalene muscles, under clavicle, over 1st rib, adjacent to subclavian artery (post & sup)
Normal MRI appearance:
Fascicles well-defined with intervening fat

56. Brachial Plexus - Normal
Cor T1
Sag T1

57. Brachial Plexopathy Pain in the shoulder radiating down arm
Etiologies: radiation >60 Gy(breast, lung ca), metastatic disease (via axillary lymphatics), direct invasion by tumor (Pancoast’s, lymphoma), direct trauma, stretch injury
MRI:
Thickened fascicles with obliteration of the intervening fat planes
Well-defined mass
With diffuse thickening of fascicles favor infiltrative neoplasm or radiation fibrosis. With well defined mass favor mets.

58. Radiation-induced Brachial Plexopathy
Which side is abnormal?

59. Radiation-induced Brachial Plexopathy
Which number corresponds to the brachial plexus?
What are the other 2 structures? 1 3 2
Subclavian artery
Subclavian vein

60. Brachial Plexus Metastasis
Cor & Sag T1

61. Brachial Plexus Metastasis
Mass
Subclavian artery
Vein
Pre and post-contrast cor T1 with fat sat

62. Shoulder – Normal Anatomy
Rotator cuff
Long head of the biceps brachialis tendon – intertubercular and intracapsular portions
AC joint/impingement
Glenoid labrum – triangular low signal on all sequences, serves to deepen glenoid fossa thereby stabilizing GH joint, attachment site of long head of biceps
Myxoid degeneration, labral tear (alphabet soup), Bankart lesion
Best evaluated with MR arthrography
Shoulder MRI most commonly ordered for the evaluation of these structures. Of course there are other things we see and look at.

63. Normal Anatomy
Normal rotator cuff, intra-articular and intertubercular long head of biceps, biceps anchor point.
No contrast in subacromial/subdeltoid bursa.
Normal communication of biceps tendon sheath with joint.

64. Rotator Cuff Tear
Supraspinatus, infraspinatus, teres minor, subscapularis
Pts > 40 yo, insidious onset of pain
Spectrum: tendinopathy, partial and full thickness tear
Etiology: degeneration (age, overuse, impingement), trauma, collagen vascular disease
MRI:
Tendinopathy – thickened tendon, increased signal on PD, intermed on T2
Partial tear – increased signal on T2, defect does not extend through cuff
Complete tear – increased signal defect on T2 extending through RC from articular surface to bursal surface; fluid in subacromial/subdeltoid bursa
Chronic tear – muscle atrophy
Impingement – shape or configuration of acromion, AC joint DJD, mass etc…

65. Rotator Cuff Tear Supraspinatus

66. Rotator Cuff Tear Supraspinatus

67. Supraspinatus Tendinopathy
Underlying degenerated tendon as evidenced by thickening and abnormal signal

68. Labral Tear Young pts <40 yo, pain, instability
Best evaluated with MR arthrogram
MRI:
Linear high T2 signal within substance of labrum
Diffuse high signal (crush injury)
Absent or small labrum
Detached labrum
Mimics:
Undercutting of articular cartilage between labrum and glenoid
Interposed synovial recess (sulcus)
Sublabral foramen/hole (detached anterosuperior labrum)

69. Labral Tear

70. Labral Tear? NO Undercutting of cartilage between labrum & glenoid
Interposed synovial sulcus
Contrast follows contour of glenoid (points medially)

71. Hillsach’s and Bankart Lesions
History of anterior shoulder dislocation
Hillsach’s – impaction fracture of posterior superior humeral head
Bankart – anterior inferior labral avulsion w/ rupture of periosteum, many variants
Bony Bankart – fracture of anterior glenoid
MRI:
Impaction fracture of posterosuperior humeral head (not round on 1st three axial images)
Anterior labral tear or variant (best evaluated with arthrography)
Many Bankart variants… alphabet soup.

72. Hillsach’s and ALPSA
ALPSA – anterior labroligamentous periosteal sleeve avulsion, medial displacement of labrum with periosteal stripping (intact periosteum), medialized Perthes
Perthes – normal position of labrum, periosteum stripped medially, but intact

73. Elbow – Normal Anatomy
Tendons – biceps, brachialis, triceps, common flexor and extensor origins
Ligaments – ulnar and radial collateral
Joints – elbow, proximal radioulnar
Olecranon bursa

74. Olecranon Bursitis
Painless mass following acute direct trauma or recurrent trauma; assoc with systemic dz
Distension of olecranon bursa (synovial sac) with fluid
MRI:
In superficial soft tissues adjacent to olecranon process and triceps insertion
mm – cm in size
High signal on T2, possible rim enhancement
+/- hemorrhagic debris

75. Olecranon Bursitis

76. Lateral Epicondylitis
Insidious onset of lateral elbow pain with activity
Overuse syndrome – repetitive varus stress
Chronic tendinopathy at common extensor origin, predominantly involving the extensor carpi radialis brevis tendon
Partial avulsion with scar formation
Plain film: normal or spur at lateral epicondyle
MRI:
Thickening of tendon with increased signal on T1 & T2

77. a.k.a Tennis Elbow
Tendinosis with small tear

78. Lateral Epicondylitis
Involves both deep and superficial fibers of extensor carpi radialis longus

79. Wrist – Normal Anatomy Bones – distal radius & ulna, carpus, MT’s
Joints – DRUJ, radiocarpal, intercarpal
Tendons – flexor & extensor
Nerves – median & ulnar
Ligaments – intercarpal (instability)
Masses – most common ganglion cyst

80. Status post trauma Where is the fracture?

81. Occult Distal Radius Fx